There has been rapid improvement in function of information equipment such as a personal computer in recent years. This rapid improvement has in turn increased an amount of data that a user of such information equipment handles. Users of the information equipment thus strongly hope for a mass storage recording device which can record a larger amount of data.
An example of such a mass storage recording device is a recording device including a hard disk. A hard disk is a discoid substrate having a surface which is coated with a magnetic material. A hard disk records information by means of a change caused by a magnetic recording element to a magnetization direction in a magnetic layer on the disc surface.
For production of a mass storage recording device, there is a key issue of improvement in recording density of a hard disk as a recording medium. Specifically, a conventional hard disk as mentioned above includes on a surface thereof a magnetic layer formed uniformly and continuously. Such a magnetic layer includes as a data write unit a recording mark having a jagged edge, which causes noise (transition noise) during reproduction. The noise then causes a problem that a S/N ratio (signal to noise ratio) is decreased, and that recorded information cannot be reproduced properly as a result.
Improving a recording density requires reducing a size of a recording mark itself. In a conventional hard disk, recording marks are formed in a uniformly formed magnetic layer. Thus, in a case where the size of such recording marks is reduced so as to increase a recording density, there occurs a magnetic interference between the recording marks. As a result, there occurs, for example, a problem that information cannot be recorded properly or recorded information cannot be reproduced properly.
One technique to solve the above problems is a patterned medium. A patterned medium is a magnetic recording medium which includes magnetic recording cells arranged so as to be magnetically isolated from one another. Such magnetic recording cells are formed of particles of a magnetic material which particles are regularly arranged on a surface of a nonmagnetic body so as to be evenly spaced with respect to one another. Magnetic information is recorded in the magnetic recording cells, each of which has an edge corresponding to the above-mentioned edge of a recording mark. With use of a patterned medium, it is possible to easily achieve a high S/N ratio even in a case where the recording marks are small. As such, in a case a patterned medium is used as a recording medium, it is possible to reduce (i) noise during reproduction and (ii) a magnetic interference between recording marks so as to greatly improve a recording density.
A high-density magnetic recording medium such as a patterned medium includes magnetic recording cells which are separated from one another by an extremely small pitch of approximately several tens of nanometers. This causes a problem that a recording error easily occurs due to a mere, slight shift in location between (i) a magnetic recording element included in a recording/reproduction head which is carrying out recording and (ii) a targeted magnetic recording cell. In particular, in a case where 1-bit data is recorded in each magnetic recording cell, it is difficult to correct during reproduction a recording error which has occurred in a single magnetic recording cell. Further, a magnetically isolated magnetic recording cell may become defective on its own. In a case where, for example, a magnetic recording cell becomes defective, the recording medium will include a magnetic recording cell in which no information can be recorded. This prevents the recording medium from recording information properly. In this case also, it is difficult to carry out error correction during reproduction.
In order to solve this problem, Patent Literature 1, for example, discloses a method of recording 1-bit data in a plurality of cells so that error correction can be carried out. This method thus intends to eliminate an influence of a write error.